President Bush announced he would address Congress and the nation tonight.

''I owe it to the country to give an explanation,'' the president said in the Oval Office.

Bush spoke after meeting with congressional leaders to discuss the economy, weak before the attacks and buffeted by thousands of layoffs in the airline industry and elsewhere in the eight days since.

''No question it's tough times,'' he said. ''This is a shock to the economy and we're going to respond.''

Lawmakers and the president said they had not reached a decision on what legislation was needed, and Federal Reserve Board chairman Alan Green-span was quoted as telling lawmakers earlier they should focus on restoring economic confidence and not rush into passing legislation of uncertain impact.

The president's announcement that he would go before a joint session of Congress marked a quickening in the pace of events as the administration worked on military, diplomatic and economic responses to the attacks that killed thousands.

A Pentagon official outlined the first steps of ''Operation Infinite Justice,'' the decision to send F-15s, F-16s and possibly B-1 bombers to the Persian Gulf. The aircraft will follow the deployment of air traffic control teams. In addition, an aircraft carrier left Virginia en route to joining two other carriers in the region.

''There are movements and we will see more movements,'' said the second-in-command at the Pentagon, Paul Wolfowitz.

The president devoted a portion of his day to diplomacy, beckoning all countries around the globe to contribute, some openly, some secretly to ''the long campaign'' against terrorism.''

Looking ahead to his speech, Bush said, ''I look forward to the opportunity to explain to the American people who would do this to our great country. And why.''

Officials said Bush will not ask Congress to declare war. They also cautioned against expecting the president to specify when military retaliation will occur. ''This is not a speech to announce military action,'' said Condoleezza Rice, Bush's national security adviser.

The speech will come nine days after the worst terrorist attacks in the nation's history. Hijackers seized four jetliners and flew two of them into the twin towers of the World Trade Center and a third into the Pentagon. A fourth crashed in rural Pennsylvania, apparently after passengers struggled with hijackers. The number of dead is expected to exceed 5,400.

Bush issued his call for an international effort to ''help us round up these people,'' responsible as the leader of the ruling Taliban in Afghanistan challenged assertions that Osama bin Laden masterminded the attacks. The Taliban leader called for an effort to find the real culprits.

Increasingly, administration officials said their investigation was pointing to bin Laden as their man, and made it clear that military retaliation against his al-Qaida terrorist network and nations that harbor it was only a matter of time. ''I have no doubt that military power is part of'' the government's response, Rice told reporters.

The government shut down the nation's airline system after the attacks, and even after the skies were reopened airlines have struggled with a dramatic falloff in business. The industry's decline was underscored during the day when two airlines, American and United, said that together they would lay off 40,000 employees.

Delta Airlines Chairman Leo Mullin, representing the industry, urged Congress to approve $17 billion in federal aid and loan guarantees, coupled with limits on legal liability for the deaths and destruction caused by the hijacked planes. With industry officials warning of bankruptcies if Congress doesn't help, Mullin said, ''Almost no airline is strong enough to survive for long, facing the upcoming challenges.''

Administration officials have offered little information on the timing or scope of their planned military retaliation. But the issue was very much in evidence during the day in Norfolk, Va., where the aircraft carrier USS Theodore Roosevelt departed on a previously scheduled mission to the Mediterranean. A band played ''New York, New York'' as the mighty ship left port. ''This is a scheduled deployment but it is by no means routine,'' said Rear Adm. Mark Fitzgerald. ''The events of the last week have renewed our sense of determination and our focus.'' Navy officials declined to say whether the attacks had changed the orders of either the aircraft carrier or the rest of its battle group.

Bush made his remarks about coalition-building in an Oval Office conversation with Indonesian President Megawati Sukarnoputri, leader of the world's most populous Muslim nation.

''We fully understand that some nations will be comfortable supporting overt activities, some nations will be comfortable supporting covert activities. Some nations will only be comfortable with providing information. Others will be helpful and will only be comfortable supporting financial matters. I understand that.''

''My message to all nations is we look forward to full cooperation,'' Bush said.

The president added that the ''first objective of a long campaign'' is to bring to justice those responsible for last week's attacks.

It was difficult to tell which of Bush's categories of open or secret help applied to Pakistan, one of a few nations on the globe with formal ties to the Taliban rulers of Afghanistan. Pakistan has been a site of anti-American rallies in recent days, yet also is a recipient of public requests by the United States to help bring bin Laden to trial.

In a nationally televised speech to his country, Pakistani President Pervez Musharraf said the United States sought help on intelligence gathering, help with logistics and permission to use Pakistan's airspace.

Taliban leader Mohammed Omar was reported to speak dismissively about previous administration remarks about bin Laden. ''Afghanistan does not have resources, nor is Osama that powerful, nor does he have contacts with the outside world to carry out or plan such attacks,'' Omar said. His remarks were reported by the Afghan Islamic Press, a Pakistan-based Afghan news agency with ties to the Taliban.